#include <iostream>
#include "stldemo/include/calculator.h"

using namespace std;

int main()
{
    int a = 10;
    int b = 20;
    cout << "a + b = " << add(a, b) << endl;
    cout << "a - b = " << sub(a, b) << endl;
    printf("hello world!\n");
    return 0;
}